This invention concerns a method for protecting living organisms against ionizing radiation, and more particularly involves the administration of high molecular weight radiation protecting agents to living organisms to protect them against ionizing radiation.
In the early 1950s it was found that cysteamine and related aminoalkyl thiols could protect living organisms against ionizing radiation. In particular, when these substances were given to mice prior to exposure to x-rays, the substances reduced the lethal effect of the x-ray radiation. Since that time, searches have been underway to discover better radiation protecting agents. Prior to making the invention disclosed in the present application, the most promising agent was WR2721 (S-2(3-Aminopropylamino)-Ethyl-Phosphorothioic Acid), which breaks down in the body to an aminoalkyl thiol, and its effect is similar to that of cysteamine.
Radiation protecting agents are useful for treating people who are likely to be exposed to radiation including workers associated with atomic reactors, military personnel, and astronauts who may be exposed while in orbit to a sudden burst from a solar flare. Radiation protecting agents are also useful as adjuncts in the radiotherapy of cancer in which the radiation protecting agents will selectively protect normal tissue allowing the cancerous tissue to be destroyed by the radiation therapy. The radiation protecting agents, to date, however, have many shortcomings including high toxicity in humans and very limited degree of protection.